McSally hasn't made a formal announcement of her intention to run in next year's Republican primary. But Arizona Rep. David Schweikert said Tuesday that she told fellow Arizona GOP members of Congress that she was running.

McSally would face off against former state Sen. Kelli Ward and could face other Republicans. Ward challenged Sen. John McCain last year.

Democratic Rep. Kyrsten Sinema is seeking her party's nomination along with several lesser-known Democrats.

Flake announced last month that he would not seek re-election. He has been an outspoken critic of President Donald Trump and acknowledged that he could not win a GOP primary in the current political climate.